1. Field of Invention
This invention relates to OLED displays and in particular to testing the integrity of the connection of driver circuits to the OLED
2. Description of Related Art
One of the more difficult tasks in forming OLED (organic light emitting diode) display modules is the attachment of driver chips to the substrate, such as glass. The attachment process uses anisotropic glue, which is to provide contact between signal and power contacts. The major source of problems are with open contacts and shorts between adjacent contacts. The method of determining a good process has been by visual inspection either by the human eye or by image processing equipment, such as cameras. Visual inspection by a human eye is prone to error and provides limited data for yield improvement. Visual inspection with image processing equipment is expensive, complicated and difficult to reproduce.
U.S. Pat. No. 7,336,035 B2 (Koyama) is directed to a OLED light emitting device wherein a current mirror circuit is formed to control drive current and luminance. In U.S. Pat. No. 7,196,536 B2 (Nystrom et al.) a method and apparatus is directed to non-contact electrical probes using corona discharge for testing OLED panels. In U.S. Pat. No. 7,123,043 B2 (Ysai et al.) a method and apparatus is directed to testing a plurality of driver circuits of an AMOLED before OLED devices are implanted by using data lines, scan lines and the power line of the AMOLED. U.S. Pat. No. 7,122,970 B2 (Ono et al.) is directed to a method for testing an OLED substrate including a switching element connected to a signal line. In U.S. Pat. No. 7,116,295 B2 (Shih) a method and system is directed to testing a plurality of driver circuits of an AMOLED where the drivers are connected to the OLED after the OLED is formed and is connected to a test element to form a loop during testing and wherein the drivers are tested one at a time. U.S. Pat. No. 7,091,738 B2 (Nakano et al.) is directed to an inspection system for inspecting characteristics of an active matrix panel before formation of an OLED, which includes a roller contact probe. U.S. Pat. No. 6,965,361 B1 (Sheats et al.) is directed to an OLED having a plurality of light emitting pixels, an isolation transistor and a driver circuit where connection points are bonded to corresponding second electrodes by a bonding layer.
In U.S. Pat. No. 6,946,307 B2 (Shih) a method and system is directed to testing circuits of an AMOLED before implantation of the OLED, wherein each circuit includes a connection to the OLED after the OLED is implanted and is configured as a test point. U.S. Pat. No. 6,859,052 B1 (Vaucher) is directed to the electrical test of electrical interconnections on a substrate by means of non-contact testing. U.S. Pat. No. 6,734,636 B2 (Sanford et al.) is directed to a method for driving an OLED comprising a first signal to set the state of a pixel circuit and a second signal to view the state. US Patent Application Publication US 2005/0078057 (Chang et al.) is directed to a display panel comprising a plurality of gate lines, data lines, switching elements, pixel electrodes, test pads, and a gate driver for generating gate signals to be applied to gate lines. In US Patent Application Publication US 2004/0239598 A1 (Koyama) a testing method is directed to active matrix display devices by checking a TFT substrate before depositing EL material and using a capacitor connected to a driver TFT in a pixel portion by visually observing the charging and discharging of the capacitor. In US Patent Application Publication US 2004/0201372 (Tsai et al) a method and apparatus is directed to testing the plurality of driver circuits of an AMOLED before the OLED is installed. In an article by Akatsu et al titled “OLED Failure Analysis and Pinpoint Shot Repair of Fault using an Optical Coaxial System of High Sensitive CCD and a Laser”, by Mitsutoshi Akatsu, Naganori Tsutsui, Nobuthito Miura and Yoshihiro Miyazaki, SID Symposium Digest 37, 426 2006 discusses detecting and repair using an optical coaxial system.